1. Field
The following description relates to an optical pickup device, and more particularly, to an optical collimator assembly having an improved driving structure and an optical pickup device including the same.
2. Description of the Related Art
Optical drives are configured to optically write information or data to a rotating medium and to read the information or data from the medium. In an optical drive, precise focusing an objective lens that faces a rotating medium is a factor that determines the quality of written and reproduced information. When writing information or data to an optical disc, a thickness between a recording layer and a surface of a disc of any of Blu-ray discs (BDs), high density-digital versatile discs (HD-DVDs), CH-DVDs, and the like that use a light source emitting light having a wavelength of 405 nm (0.1 mm) is smaller than a thickness of any of compact discs (CDs) and DVDs (0.6 mm). Such a thickness difference causes spherical aberration. When spherical aberration increases, a reproducing performance of optical drives is lowered due to an effect of adjacent pits. Further, precise pits cannot be generated during a writing operation. Thus a writing performance of optical drives is also lowered.
Thus, correction of spherical aberration needs to be performed so as to maintain writing and reproducing performances of an optical system. In particular, the importance of aberration correction increases in an optical data storage (ODS) for realizing high definition, such as BDs, HD-DVDs, and the like.
To this end, a collimating lens is often used in an optical disk drive for aberration correction. The collimating lens may be movable on an optical axis. A collimator assembly is a combination of several components including a collimating lens, a lens holder, an actuator for driving the collimating lens, and a structure for supporting the collimating lens, the lens holder, and the actuator.
A stepping motor or a piezoelectric motor is generally used as an actuator for driving a collimating lens. However, in situations where a rotation type stepping motor is configured to have a small size, a torque of the stepping motor decreases. Thus, it is not advantageous to miniaturize a rotation type stepping motor to a predetermined size.
On the other hand, a piezoelectric motor has a structure that performs a simple reciprocating motion using deformation (i.e., contraction and expansion) of a piezoelectric body and requires a high voltage of more than 50 V. Thus, a piezoelectric motor causes an electrical design burden. In addition, a reciprocating motion shaft that supports a collimating lens is mechanically weak.